A FINITE-ELEMENT MODEL FOR THERMOMECHANICAL ANALYSIS IN CASTING PROCESSES

This paper summarizes the recent work of the authors in the numerical simulation of casting processes. In particular, a coupled thermomechan ical model to simulate the solidification problem in casting has been developed [7,8,9]. The model, based on a general isotropic thermoelast o-plasticity theory and formulated in a macroscopical point of view, i ncludes generalized phase-change effects and considers the different t hermomechanical behaviour of the solidifying material during its evolu tion from liquid to solid. For this purpose, a phase-change variable, plastic evolution equations and a temperature-dependent material const itutive law have been defined. Some relevant aspects of this model are presented here. Full thermomechanical coupling terms have been consid ered as well as variable thermal and mechanical boundary conditions: t he first are due to air gap formation, while the second involve a cont act formulation. Particular details concerning the numerical implement ation of this model ale also mentioned. An enhanced staggered scheme, used to solve the highly non-linear fully coupled finite element equat ions, is proposed. Furthermore, a proper convergence the quadratic con vergence of Newton-Rapshon's method is not achieved, several numerical experiments demonstrate reasonable convergence rates [9]. Finally, an experimental cylindrical casting test problem, including phase-change phenomena, temperature-dependent constitutive properties and contact effects, is analyzed. Numerical results are compared with some laborat ory measurements.